get Variable product SKU in Contact Form 7

Hello,

I want to attach product SKU in for product variation in Contact Form 7.
However I am able to get simple product SKU in function.php file , craete shortcode for it & attach it to CF7.
But not possible with variation sKU.
Can anyone let me know how I should achieve this?

Code below for simple SKU is working.

function custom_get_product_sku( $atts ) {
	
	global $product;
		
	$atts = shortcode_atts( array(
        	'id'  =>  '',
    	), $atts );
  
  	// If no id, we're probably on a product page already
  	if ( empty( $atts['id'] ) ) {
		
		$sku = $product->get_sku();
		
	} else {
		
		//get which product from ID we should display a SKU for
		$product = wc_get_product( $atts['id'] );
	  	$sku = $product->get_sku();
		
	}

	ob_start();
	
	//Only echo if there is a SKU
	if ( !empty( $sku ) ) {
		echo $sku;
	}
	
	return ob_get_clean();
	
}
add_shortcode( 'wc_sku', 'custom_get_product_sku' );

Help Me ASAP please.

Thanks in advance!